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United States Patent |
5,153,086
|
Yagi
,   et al.
|
October 6, 1992
|
Electrophotographic photoreceptor with charge transport layer of silicon
oxide, carbide or nitride and transition metal
Abstract
An electrophotographic photoreceptor essentially comprising a substrate
having thereon a charge transporting layer and a charge generating layer
is disclosed, wherein said charge transporting layer comprises at least
one of silicon oxide, silicon carbide, and silicon nitride and contains a
transition metal element. The photoreceptor exhibits stable
electrophotographic characteristics on repeated use and prolonged
durability.
Inventors:
|
Yagi; Shigeru (Kanagawa, JP);
Watanabe; Masao (Kanagawa, JP)
|
Assignee:
|
Fuji Xerox Co., Ltd. (Tokyo, JP)
|
Appl. No.:
|
648790 |
Filed:
|
February 1, 1991 |
Foreign Application Priority Data
Current U.S. Class: |
430/58.1; 430/66 |
Intern'l Class: |
G03G 005/047 |
Field of Search: |
430/58,60,66
|
References Cited
U.S. Patent Documents
4733482 | Mar., 1988 | West et al. | 357/23.
|
4876168 | Oct., 1989 | Hotomi et al. | 430/58.
|
5041350 | Aug., 1991 | Yagi | 430/58.
|
Primary Examiner: Martin; Roland
Attorney, Agent or Firm: Finnegan, Henderson, Farabow, Garrett and Dunner
Claims
We claim:
1. An electrophotographic photoreceptor essentially comprising a substrate
having thereon a charge transporting layer and a charge generating layer,
wherein said charge transporting layer comprises at least one of silicon
oxide, silicon carbide, and silicon nitride and contains a transition
metal element, wherein said transition metal element is present in an
amount of from 0.01 to 30 at. % based on silicon.
2. An electrophotographic photoreceptor as claimed in claim 1, wherein said
transition metal element is selected from 3d, 4d, and 5d transition metal
elements.
3. An electrophotographic photoreceptor as claimed in claim 1, wherein said
transition metal element is selected from the group consisting of Sc, Ti,
V, Cr, Mn, Fe, Co, Ni, Cu, and Zn.
4. An electrophotographic photoreceptor as claimed in claim 1, wherein said
charge transporting layer has an electrical resistance of from 10.sup.11
to 10.sup.16 .OMEGA..cm.
5. An electrophotographic photoreceptor as claimed in claim 1, wherein said
silicon oxide has an oxygen to silicon atomic ratio of from 0.1 to 2.0.
6. An electrophotographic photoreceptor as claimed in claim 1, wherein said
silicon carbonate has a carbon to silicon atomic ratio of from 0.05 to
1.0.
7. An electrophotographic photoreceptor as claimed in claim 1, wherein said
silicon nitride has a nitrogen to silicon atomic ratio of from 0.1 to 1.3.
Description
FIELD OF THE INVENTION
This invention relates to an electrophotographic photoreceptor and, more
particularly, to a charge transporting layer of an electrophotographic
photoreceptor having a function separated type photosensitive layer.
BACKGROUND OF THE INVENTION
A so-called function separated type electrophotographic photoreceptor has a
photosensitive layer composed of a charge generating layer capable of
generating a photo carrier on exposure to light and a charge transporting
layer capable of efficiently transporting the thus-generated photo
carrier. Charge transporting materials which have hitherto been employed
include organic materials, such as high-molecular weight compounds (e.g.,
polyvinylcarbazole) and high-molecular weight resin binders (e.g.,
polycarbonate) having dispersed or dissolved therein low-molecular weight
compounds (e.g., pyrazoline and triphenylamine); and inorganic materials,
such as chalcogen compounds (e.g., selenium and selen-tellurium).
However, electrophotographic photoreceptors using these conventional charge
transporting materials have disadvantages such that electrical
characteristics such as chargeability, dark decay, residual potential, and
the like are instable against repeated use and that the photosensitive
layer has insufficient mechanical strength, i.e., hardness or adhesion,
and is liable to receive scratches in a copying machine or undergo layer
separation. Therefore, the photoreceptors have difficulty in producing
satisfactory copies for a long time in a stable manner, and their working
life (durability) has been limited to thousands to tens of thousands of
copies.
Where a surface layer or an adhesive layer is additionally provided to
overcome these problems, the structure of a photosensitive layer becomes
overly complicated, rather resulting in an increase of defects during
production of the photoreceptor.
Further, electrophotographic photoreceptors using organic charge
transporting materials are inferior in transporting performance,
particularly potential decay in a low temperature environment, and, also,
unsuitable for high-speed copying.
Furthermore, electrophotographic photoreceptors using conventional charge
transporting materials have insufficient stability to heat or light and
easily undergo deterioration such as crystallization or degradation of
low-molecular weight compounds. It has thus been necessary to control the
conditions or environment in which the photoreceptors are used or stored.
In function separated type electrophotographic photoreceptors having a
charge transporting layer on a part of a photoconductive layer, the charge
transporting layer generally has a small thickness and therefore shows
reduced light absorption at wavelengths near the absorption ends, that is,
light passing through the charge transporting layer increases. As a
result, an interference fringe unavoidably appears due to multiple
reflected light from a substrate particularly when in using an infrared
laser as a light source.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a highly durable
electrophotographic photoreceptor having a novel charge transporting layer
having high adhesion, high mechanical strength or hardness, and reduced
defects.
Another object of the present invention is to provide an
electrophotographic photoreceptor which has high sensitivity, superior
panchromatic properties, high chargeability, small dark decay, and low
residual potential after exposure.
A further object of the present invention is to provide an
electrophotographic photoreceptor which produces high quality images free
from an interference fringe when used in a laser printer using coherent
light, e.g., infrared semi-conductor laser light, as a light source.
The inventors have found that incorporation of a transition metal element
into silicon oxide, silicon carbide or silicon nitride provides a charge
transporting material having excellent charge transporting function and
that a function separated type photoreceptor using such a charge
transporting material exhibits greatly improved physical, chemical,
mechanical and optical properties over those using conventional charge
transporting materials, and thus reached the present invention.
The present invention relates to an electrophotographic photoreceptor
essentially comprising a substrate having thereon a charge transporting
layer and a charge generating layer, wherein said charge transporting
layer comprises at least one of silicon oxide, silicon carbide, and
silicon nitride and contains a transition metal element.
BRIEF DESCRIPTION OF THE DRAWING
FIGS. 1 and 2 are a schematic cross section illustrating an essential
structure of the electrophotographic photoreceptor according to the
present invention, in which the numerals 1, 2, and 3 indicate a substrate,
a charge transporting layer, and a charge generating layer, respectively.
FIG. 3 is a schematic cross section illustrating one embodiment of the
electrophotographic photoreceptor according to the present invention, in
which the numerals 4 and 5 indicate an intermediate layer such as a charge
blocking layer and a surface protective layer, respectively.
DETAILED DESCRIPTION OF THE INVENTION
Supports which can be used in the present invention may be either
electrically conductive or insulating. Suitable conductive substrates
include metals and alloys, e.g., aluminum, stainless steel, nickel, and
chromium. Suitable insulating substrates include films or sheets of high
polymers, e.g., polyester, polyethylene, polycarbonate, polystyrene,
polyamide, and polyimide; glass, and ceramics. The surface of insulating
substrates at least on the side having a photosensitive layer must be
rendered electrically conductive by, for example, vacuum evaporation,
sputtering or ion plating of metals, such as the above-mentioned metals,
gold, copper, etc. The electrophotographic photoreceptor of the invention
may be irradiated with an electromagnetic wave either from the side of the
support or from the side of the photosensitive layer. In the former case,
when the above-mentioned metal is used for imparting conductivity, the
thickness of the support should be such that permits of transmission of
the electromagnetic wave. A transparent conductive film, e.g., indium-tin
oxide (ITO), may be made use of for rendering the surface of a substrate
conductive.
The charge transporting layer according to the present invention may be
provided at a position either closer to or farther from the substrate than
a charge generating layer.
In the charge transporting layer according to the present invention, charge
transporting is effected through hopping conduction of photo carriers
among transition metal particles present in a silicon oxide, carbide or
nitride matrix. It is considered that the d atomic orbital possessed by
the metallic element contributes to charge transporting. In the present
invention, satisfactory charge transporting properties can be obtained
when the charge transporting layer has an electrical resistance of from
10.sup.11 to 10.sup.16 .OMEGA..cm.
The transition metal elements which are incorporated into a charge
transporting layer include 3d, 4d, and 5d transition metal elements. Of
these elements, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, or Zn of 3d transition
metal elements whose d-electrons are distributed near to the nucleus with
small orbital radii and have proper directionality are particularly
preferred. When these elements are incorporated into silicon compounds,
the degree of overlap of atomic orbits among transition metal elements is
small, and the elements are easily localized, making it easy to control
dark conductivity and transporting capacity.
The charge transporting layer mainly comprising at least one of silicon
oxide, silicon carbide (preferably silicon oxide), and silicon nitride can
be formed by gaseous phase deposition methods such as PVD (physical vapor
deposition), e.g., CVD, plasma CVD, and ion plating; or liquid phase
deposition methods such as a sol-gel method and electrodeposition. A
transition metal element can be incorporated into the silicon compound
deposit by simultaneous deposition using a mixed raw material or by
separately decomposing two raw materials on a support. It is also possible
that a layer of a silicon compound is once formed and then a transition
metal element is incorporated thereinto by ion striking, penetration or
impregnation.
Silicon oxide to be formed suitably has an oxygen to silicon atomic ratio
of from 0.1 to 2.0 and preferably from 0.2 to 2.0. Silicon carbide to be
formed suitably has a carbon to silicon atomic ratio of from 0.05 to 1.0
and preferably from 0.1 to 1.0. Silicon nitride to be formed suitably has
a nitrogen to silicon atomic ratio of from 0.1 to 1.3 and preferably from
0.2 to 1.3. If an atomic ratio of oxygen, carbon or nitrogen to silicon in
silicon oxide, carbide or nitride is less than 0.1, electrical resistance
is too low to retain sufficient quantity of charge.
The transition metal element is added in an amount of from 0.01 to 30 at.
%, and preferably from 1 to 20 at. %, based on silicon. If the transition
metal content is less than 0.01 at. %, the layer cannot perform an
effective transporting function. If it is more than 30 at. %, the layer
has too low resistance to retain sufficient quantity of charge. The
incorporated transition metal element may be distributed in the silicon
compound either uniformly or non-uniformly, forming secondary or tertiary
particles.
A typical example of the formation of the charge transporting layer
according to the present invention is described below.
In the case of plasma CVD, a vaporized silicon compound is introduced into
a vacuum reactor, and an electric field is applied between two electrodes
at a frequency of from 0 to 5 GHz while maintaining the inner pressure at
10.sup.-4 to 10.sup.-5 Torr to cause an electrical discharge. There is
thus formed a deposit on an electrode substrate or a substrate placed on
an electrode and heated to 20.degree. to 400.degree. C. Raw materials as a
silicon source include SiCl.sub.4, SiH.sub.4, and Si.sub.2 H.sub.6
(preferably SiH.sub.4), and raw materials to be reacted with silicon to
form an oxide, carbide or nitride (preferably oxide and nitride) include
O.sub.2, CO.sub.2, N.sub.2 O, CH.sub.4, C.sub.2 H.sub.6, N.sub.2,
NH.sub.3, and NHNH (preferably O.sub.2). Raw materials for transition
metal elements include organometallic compounds, e.g., CrF.sub.3,
CrF.sub.4, ZrF.sub.4, TiF.sub.4, CuF.sub.2, NiF, VF.sub.3, MnF.sub.2,
MoF.sub.6, MoCl.sub.6, WF.sub.6, WCl.sub.6, Zn(CH.sub.3).sub.2, and
Zn(C.sub.2 H.sub.5).sub.2. The organometallic compound as a transition
metal element source is introduced in a gaseous phase into the vacuum
reactor as a gaseous mixture with the above-described raw material gas or
separately from the above-described raw material gas. If desired, a
carrier gas, e.g., hydrogen, nitrogen, helium, and argon, may be used in
combination.
In the case of ion plating, silicon or silicon oxide, carbide or nitride is
used as a silicon source. The degree of vacuum in a vacuum chamber is set
at 10.sup.-5 to 10.sup.-7 Torr The silicon source is melted and vaporized
by means of an electron gun at a voltage of from 0.5 to 50 kV and a
current of from 1 to 1000 mA while applying a voltage of +1 to 500 V to
the ionizing electrode and a bias voltage of +0 to -2000 V to the
substrate, and the evaporated atom and/or ion is reacted with an O, C or N
atom, ion or molecule in an activated O.sub.2, N.sub.2, CO.sub.2,
CH.sub.4, or NH.sub.4 plasma by a glow discharge and the like to obtain an
oxide, carbide or nitride of silicon (preferably oxide of silicon). The
reaction pressure is in the range of from 10.sup.-6 to 10.sup.-1 Torr, and
preferably from 10.sup.-4 to 10.sup.-2 Torr. Incorporation of a transition
metal element into the produced silicon compound can be carried out by
simultaneously heat-evaporating a transition metal element or a compound
thereof from a separate evaporation source by means of an electron gun or
a like technique. Transition metal element sources include Sc, Ti, V, Mn,
Cr, Fe, Co, Ni, Cu, Zn, TiO.sub.2, ZrO.sub.2, Fe.sub.2 O.sub.3, CoO, NiO,
WC, TiC, CuO, ZrC, ScC, and TiN.
In the case of a sol-gel method, a silicon alkoxide, e.g.,
Si(OCH.sub.3).sub.4, Si(OC.sub.2 H.sub.5).sub.4, Si(OC.sub.3
H.sub.7).sub.4 and Si(OC.sub.4 H.sub.9), is dissolved in an alcohol and
hydrolyzed while stirring. The resulting sol is applied to a substrate by
spraying or dip-coating. After the solvent is removed, the coating is
dried by heating at 50.degree. to 300.degree. C. for 1 to 24 hours to
obtain silicon oxide. A transition metal element can be incorporated by
adding a transition metal alkoxide, e.g., Ti(OC.sub.3 H.sub.7).sub.4,
Zr(OC.sub.3 H.sub.7).sub.4, Y(OC.sub.3 H.sub.7).sub.3 Y(OC.sub.4
H.sub.9).sub.3, Fe(OC.sub.2 H.sub.5).sub.3, Fe(OC.sub.3 H.sub.7).sub.3,
Fe(OC.sub.4 H.sub.9).sub.3, Nb(OCH.sub.3).sub.5, Nb(OC.sub.2
H.sub.5).sub.5, Nb(OC.sub.3 H.sub.7).sub.5, Ta(OC.sub.3 H.sub.7).sub.5,
Ta(OC.sub.2 H.sub.9).sub.5, V(OC.sub.2 H.sub.5).sub.5, and V(OC.sub.4
H.sub.9 ).sub.3, or an organic transition metal complex, e.g.,
trisacetylacetonatoiron, bisacetylacetonatocobalt,
bisacetylacetonatonickel, and bisacetylacetonatocopper, to the
above-described sol.
Among these method for forming the charge transporting layer, the sol-gel
method is preferred.
The thus formed silicon oxide, carbide or nitride functions like a binder
resin in an organic low-molecular weight compound-dispersion type charge
transporting layer. The transition metal element appears to serve as a
low-molecular weight substance providing sites of charge transporting.
The thickness of the charge transporting layer is a range of from 2 to 100
.mu.m, and preferably from 3 to 50 .mu.m.
A charge generating layer which can be used in the present invention can be
made of inorganic substances, e.g., amorphous silicon, selenium, arsenic
selenide, and selen-tellurium, by CVD, vacuum evaporation, sputtering or a
like technique. A charge generating layer can also be made of a thin film
of dyestuffs, such as phthalocyanine, Cu-phthalocyanine,
Al-phthalocyanine, V-phthalocyanine, squaric acid derivatives, merocyanine
dyes, and bisazb dyes, which is formed by vapor deposition or by applying
a dispersion of these dyestuffs in a binder resin by dip coating or the
like method.
In particular, a charge generating layer made of hydrogenated amorphous
silicon, germanium-doped hydrogenated amorphous silicon, or hydrogenated
amorphous germanium exhibits excellent mechanical and electrical
characteristics.
Formation of a charge generating layer using hydrogenated amorphous silicon
for instance is explained below in detail.
A charge generating layer mainly comprising amorphous silicon can be formed
by known methods, for example, glow discharge decomposition, sputtering,
ion plating, and vacuum evaporation. While a film formation method is
appropriately selected from among them according to the end use, a method
comprising glow discharge decomposition of a silane gas or a silane-based
gas by plasma CVD is preferred. According to this method, a film
containing from 1 to 40 at. % of hydrogen and having relatively high
resistance and high photosensitivity can be formed to provide a charge
generating layer having suitable characteristics.
In the case of plasma CVD method, for instance, starting gas materials
which can be used for preparing a charge generating layer mainly
comprising silicon include silane gases, e.g., monosilane and disilane. If
desired, a carrier gas, e.g., hydrogen, helium, argon, and neon, may be
used. The starting gas may also contain a dopant gas, e.g., diborane
(B.sub.2 H.sub.6) and phosphine (PH.sub.3), to incorporate impurities,
e.g., boron and phosphorus, into a charge generating layer. Further, for
the purpose of increasing photosensitivity, a halogen atom, a carbon atom,
an oxygen atom, a nitrogen atom, etc. may be incorporated. Furthermore,
for the purpose of increasing sensitivity in the longer wavelength region,
elements, such as germanium and tin, may be added.
A charge generating layer preferably comprises silicon as a main component
and from 1 to 40 at. %, and particularly from 5 to 20 at. %, of hydrogen.
The thickness of the charge generating layer is from 0.1 to 30 .mu.m, and
preferably from 0.2 to 10 .mu.m.
If desired, the electrophotographic photoreceptor according to the present
invention may additionally have other optional layers on or beneath the
set of a charge generating layer and a charge transporting layer. Such
optional layers include a charge blocking layer made of a p-type
semi-conductor or an n-type semi-conductor comprising amorphous silicon
doped with an element of the group III or V of the periodic table, an
insulating layer containing silicon oxide, silicon carbide, silicon
nitride, or amorphous carbon, and a layer for controlling adhesion or
electrical and image-formation characteristics which is made of a p-type
semi-conductor or an n-type semi-conductor comprising amorphous silicon
doped with an element of the group III or V of the periodic table, or
which contains oxygen, carbon or nitrogen. The thickness of these layers
is arbitrarily decided, usually of from 0.01 to 10 .mu.m and preferably
from 0.1 to 2.0 .mu.m.
A surface protective layer may be provided in order to prevent denaturation
of the surface of a photoreceptor due to corona ions. The thickness of the
surface protective layer is generally from 0.1 to 10 .mu.m and preferably
from 0.5 to 5 .mu.m.
Each of the above-described optional layers can be formed by plasma CVD
method. As stated with respect to a charge generating layer, impurity
elements can be incorporated, if desired, by introducing a vaporized
substance containing a desired impurity element into a plasma CVD
apparatus together with a silane gas to conduct glow discharge
decomposition. Film forming conditions for these layers are as follows.
The frequency is usually from 0 to 5 GHz, and preferably from 5 to 3 GHz;
the discharge pressure is from 10.sup.-5 to 5 Torr (0.001 to 665 Pa); and
the substrate heating temperature is from 100.degree. to 400.degree. C.
The present invention is now illustrated in greater detail by way of
Examples, but it should be understood that the present invention is not
deemed to be limited thereto.
EXAMPLE 1
In a glass container with a stopper (i.e., a plug) were charged 20 g of
water and 50 g of ethanol, and the solution was stirred. To the solution
was added 70 g of Si(OC.sub.3 H.sub.7).sub.4, followed by stirring for 60
minutes to conduct hydrolysis. Then, 7 g of Zr(OC.sub.4 H.sub.9).sub.4 was
added thereto and mixed with stirring. After adjusting the viscosity by
concentration, the mixture was dip-coated on a 2 mm thick aluminum plate
and dried at a temperature increasing from 100.degree. C. to 300.degree.
C. in three steps to form a 8 .mu.m thick film containing Zr and mainly
comprising SiO.sub.x.
The aluminum plate having thereon the Zr-containing SiO.sub.x film was set
in a vacuum chamber of a capacitively-coupled type plasma CVD apparatus.
The substrate temperature was maintained at 250.degree. C., and 100%
silane gas (SiH.sub.4) and 100 ppm (hydrogen-diluted) diborane gas
(B.sub.2 H.sub.6) were introduced into the chamber at a rate of 100 ml/min
and 2 ml/min, respectively. After setting the inner pressure at 0.5 Torr,
a high-frequency electrical power of 13.56 MHz was imposed to induce a
glow discharge, and the power was maintained at 100 W. There was thus
formed a 1 .mu.m thick charge generating layer having high dark resistance
which comprised so-called i-type amorphous silicon containing hydrogen and
a trace amount of boron. Subsequently, the chamber was evacuated to a high
degree of vacuum, and 30 sccm (i.e., standard cubic centimeter per
minutes: cm.sup.3 /min) of SiH.sub.4 and 30 sccm of NH.sub.3 were
introduced thereinto. A discharge was effected at a power of 50 W to form
a 0.1 .mu.m thick SiN.sub.x film. There was thus produced an
electrophotographic photoreceptor having an about 9 .mu.m thick
photosensitive layer.
Electrophotographic characteristics of the resulting photoreceptor were
evaluated as follows. An initial surface potential after charging to +6 kV
by means of a corotron discharger was 400 V. A residual potential after
exposure to light of 500 nm was 30 V. The photosensitivity was 6
erg/cm.sup.2 as expressed in terms of a half-decay exposure amount (i.e.,
exposure required for the half decay of the surface potential).
EXAMPLE 2
An arc discharge type ion plating apparatus equipped with a resistance
heating source and an electron beam heating means was used 99.99% purity
Si was put in a first crucible, and Ti was put in a second crucible. The
vacuum chamber was evacuated to 10.sup.-4 Pa by means of an oil diffusion
pump, and Si and Ti were simultaneously vaporized by using two 3 kW
electron guns while heating a thermionic filament to emit thermions of
about 60 A. Ionization was conducted at an ionizing electrode voltage of
60 V.
N.sub.2 was introduced from the lower part of the thermionemitting
electrode, and the pressure was set at 6.times.10.sup.-2 Pa. The ionized
Ti and Si were thus reacted with N.sub.2 to form a 8 .mu.m thick charge
transporting layer containing Ti and mainly comprising SiN on a 1 mm thick
stainless steel substrate to which a bias of -500 V was applied.
The substrate having thereon the charge transporting layer was taken out of
the vacuum chamber and set in a parallel plate type plasma CVD apparatus.
Subsequently, the chamber was evacuated, and a charge generating layer and
a surface layer were formed on the charge transporting layer under the
same conditions as in Example 1.
When the resulting electrophotographic photoreceptor was charged to +6 kV
with a corotron discharger, a surface potential of 450 V was maintained. A
residual potential after exposure to light of 500 nm was 15 V.
EXAMPLE 3
The same ion plating apparatus as used in Example 2 was used. A mixed
powder comprising SiO.sub.2 and 5% by weight of Cu was put in a crucible.
Oxygen gas was introduced into the chamber, and the pressure was set at
6.times.10.sup.-2 Pa. The starting mixed powder was vaporized and ionized
under conditions of 2 kW in power of the electron gun, 100 mA in
ionization current, and -200 V in bias applied to a substrate to form a 10
.mu.m thick Cu-containing SiO.sub.x film on an aluminum substrate kept at
200.degree. C.
The substrate having thereon the charge transporting layer was taken out of
the vacuum chamber and set in a parallel plate type plasma CVD apparatus.
The chamber was evacuated, and a charge generating layer and a surface
layer were formed thereon under the same conditions as in Example 1.
When the resulting electrophotographic photoreceptor was charged to +6 kV
with a corotron discharger, an initial surface potential of 400 V was
maintained. A residual potential after exposure to light of 500 nm was 20
V.
EXAMPLE 4
An arc discharge type ion plating apparatus equipped with a resistance
heating source and an electron beam heating means was used. 99.99% purity
Si was put in a crucible for resistance heating, and Ti was put in a
center crucible. The vacuum chamber was evacuated to 10.sup.-4 Pa by means
of an oil diffusion pump, and Ti was vaporized by using a 3 kW electron
gun while vaporizing Si by resistance heating. A thermionic filament was
heated to emit thermions of about 60 A. Ionization was conducted at an
ionizing electrode voltage of 50 V.
C.sub.2 H.sub.2 was introduced from the lower part of the thermionic
emitting electrode, and the pressure was set at 2.times.10.sup.-2 Pa. The
ionized Ti and Si were thus reacted with C.sub.2 H.sub.2 to form a 8.5
.mu.m thick charge transporting layer containing Ti and mainly comprising
SiC on a 1 mm thick stainless steel substrate to which a bias of -500 V
was applied.
The substrate having thereon the charge transporting layer was taken out of
the vacuum chamber and set in a parallel plate type plasma CVD apparatus.
The chamber was evacuated, and a charge generating layer and a surface
layer were formed under the same conditions as in Example 1.
When the resulting electrophotographic photoreceptor was charged to +6 kV
with a corotron discharger, an initial surface potential of 450 V was
maintained. A residual potential after exposure to light of 500 nm was 20
V.
As described above, the charge transporting layer according to the present
invention, comprising silicon oxide, silicon carbide, silicon nitride or a
mixture of two or more thereof and containing a transition metal element,
exhibits satisfactory adhesion between layers, high mechanical strength
and hardness while being free from defects. Accordingly, the
electrophotographic photoreceptor using such a charge transporting layer
has high durability, high sensitivity, superior panchromatic properties,
high chargeability, small dark decay, and low residual potential after
exposure. Moreover, the photoreceptor of the present invention is
employable in printing systems using coherent light as a light source,
such as an infrared semi-conductor laser, and provides a high quality
image while preventing occurrence of an interference fringe in a laser
printer.
While the invention has been described in detail and with reference to
specific examples thereof, it will be apparent to one skilled in the art
that various changes and modifications can be made therein without
departing from the spirit and scope thereof.
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